service: Use nested namespace specifiers where applicable

There were a few places where nested namespace specifiers weren't being
used where they could be within the service code. This amends that to
make the namespacing a tiny bit more compact.

src/core/hle/service/cecd/cecd.cpp

@@ -10,8 +10,7 @@
 #include "core/hle/service/cecd/cecd_s.h"
 #include "core/hle/service/cecd/cecd_u.h"
 
-namespace Service {
-namespace CECD {
+namespace Service::CECD {
 
 void Module::Interface::GetCecStateAbbreviated(Kernel::HLERequestContext& ctx) {
     IPC::RequestParser rp(ctx, 0x0E, 0, 0);
@@ -59,5 +58,4 @@ void InstallInterfaces(SM::ServiceManager& service_manager) {
     std::make_shared<CECD_U>(cecd)->InstallAsService(service_manager);
 }
 
-} // namespace CECD
-} // namespace Service
+} // namespace Service::CECD